aarghh! Nits at nursery. Can I prevent the dc's catching them?

A couple of children at nursery have nits. What do I need to know about minimising the chances of the dc's catching them? I have no idea what the drill is or what products are available in the shops these days.

Essential oils, combing with conditioner (does it have to be washed out?) or full on chemical warfare?

They are only 1 & 2 and have really fine hair if that makes any difference.

put a little tea tree oil in their shampoo, nits don't like it but it doesnt ALWAYS stop them! i use full marks shampoo (ds is 6), you put it on like ordinary shampoo, leave 10 mins and then rinse out, it usually kills the majority of them/all of them. then a comb for a night or two,

Comb every 2-3 days, that way you will find and remove all the nits and any hatched lice. I avoid chemicals for mine unless they've got a real infestation, mine also have fine hair so I find regular combing gets most of the nits and lice.

Keeping hair tied back can help - lice crawl, they can't jump, but as young children have so much head to head contact nits and lice are inevitable IME!